1. Technical Field
The present invention relates to a method of controlling a charged particle beam, such as an electron beam or an ion beam in an emittance for use in, for example, an electron beam apparatus such as an electron accelerator or an electron microscope for controlling the charged particle beam.
2. State of the Art
Generally, in an electron beam apparatus such as an electron microscope, energy of transverse thermal motion would occur within a transverse plane which is perpendicular to the direction of a beam generated by an electron gun. The transverse thermal motion can be replaced by the term "emittance" which is used in the particle optics art and which is defined as a product of an inclination angle with respect to the axial direction of the electron beam and spatial spread of the electron beam along the direction of the inclination projected on the transverse plane. Such a magnitude of the emittance determines the upper limit of a resolution of an electron microscope.
As will be obvious even from the above-mentioned fact, in order to get an electron beam of high quality, it is required to minimize an emittance of the electron beam as well as to make energy uniform by cooling the electron beam. However, a method of improving an emittance in an electron beam apparatus has not been proposed at all so far.
It is an object of the present invention to resolve this problem and to momentarily cool an electron beam regardless of a pulsed beam or a continuous beam.